I had a failure on the front cyl throttle shaft yesterday.now i thought this problem was limited to the 58mm bore shafts but no.mine are still the standard 53mm bores but running stage two cams with powerline exh.firstly, i had a cracked head then this and am wondering weather these cams are worth the unreliability i am experiencing with this motor. i have over 50000km on these cams and 70000+ on the motor,not nearly enough to call it wear and tear.Are others out there having failures also with the standard shafts/ 53mm bores?

Pecee, I have the same set up as you on my 08 Dx. However, I only have 30K miles on mine, and so far, have no problem with heads and/or throttle shafts. Also, I do ride my bike hard. The low mileage is do to splitting riding duties with a 93 Softail and a 91 FXR that eventually I sold to my buddy. A while back, I asked this same question to Scott (Ohio Vrod) and was told that no problem with the stock Tbodies. So far, that seems to be the case to my knowledge. Still, I check mine from time to time. I know this doesn't help much, wish I could give you more. Good luck, Bro.

Broken throttle shafts are caused by excessive vibrations/wear .. The buterflies were probably fluttering. With the miles on your bike & running the stage II cams I think it is just that. Service the upper end and replace the broken TB. ( I wouldn't fix it unless you rebuild the whole thing. )

I think that a long duration of stage II cams could have something to do with the saft failures. A low rpm compression pressure back flow (reversion) can cause some extra load and vibration for the safts.

Broken throttle shafts are caused by excessive vibrations/wear .. The buterflies were probably fluttering. With the miles on your bike & running the stage II cams I think it is just that. Service the upper end and replace the broken TB. ( I wouldn't fix it unless you rebuild the whole thing. )

I think that a long duration of stage II cams could have something to do with the saft failures. A low rpm compression pressure back flow (reversion) can cause some extra load and vibration for the safts.

Better watch what you say. I suggested this way back and was kicked in the ass for it.

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Sorry, did I a technical or commercial mistake?
No meaning to scare anyone.

No no! It was a joke. In the past I suggested that it was a reverberation or harmonics issue and everyone argued that fact against me. I agree with you 100%.

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No no! It was a joke. In the past I suggested that it was a reverberation or harmonics issue and everyone argued that fact against me. I agree with you 100%.

Would this be from the over-lap at idle ? Like at the split second the intake and exhaust are both opened,just before tdc,running pressure back up the intake and putting opposite force on the throttle blades.
I think this is why.cure would be stronger metal for the shafts,and or a larger diameter shaft.

Yes ,you guys are all right as to the cause im sure.I have taken the old t/body to a master machinist and discussed the issue.He is of the belief that a full shaft slotted for the butterfly will be better than the original half shaft .he is going to make new shafts in that config for me.he wasnt too keen on using tool steel tho because he felt it wouldnt stand the vibrations and probably crack too.welding was not an option.he will screw and loctite the butterflys in.no peening.

I am lucky then ,the screw was just sitting there waiting to drop...Im going to look into welding the butterfly to the shaft as an experiment.

I think Scott Tig's the screw to the shaft. Welding the butterfly to the shaft, would make this pretty much impossible to disassemble in the future.

Though I do like his idea of larger diameter shafts - which he pretty much does as part of his 58mm upgrade to stock TB's (which he can also upgrade on one's already done, and Destroyer TB's).

There is some reversion (if you want to call it that) from the higher lift/faster ramp/overlap of these cams - as evidenced by the seeming inability of (supposed) autotuners to cope with the intake charge "bleeding through" during overlap and causing the WideBands to freak out and lean the mix. Also the observation of how much noisier these cams are. There probably is more vibration and potential "puffing" against the back of the butterflies (at least more than with stock), putting extra stress on the shafts, causing premature breakage.